Menopausal Bone Loss

The loss of bone density after menopause has long been linked to the dramatic decrease
in the estrogen hormone, estradiol. But a recent series of studies in women age 40
to 55 has found that estrogen may not be the only hormone that should be considered.

“For years, the model has been that ovaries lose their ability to make a potent estrogen
at menopause, and that this estrogen decline starts the bone loss,” says epidemiologist
MaryFran Sowers, the John G. Searle Professor of Public Health at the University of
Michigan.

However, data from the Study of Women’s Health Across the Nation (SWAN), a long-term
study of over 3,000 multiethnic women, is showing that bone loss begins before the
onset of menopause and before estrogen levels have really started to decline.

Sowers’s team zeroed in on follicle-stimulating hormone, FSH for short, as another
culprit contributing to bone density loss. FSH is produced in the pituitary gland
of the brain and serves as a messenger to the ovaries to produce sex hormones. Levels
of this hormone begin to rise and become increasingly higher in the peri-menopause,
well before the estrogen dip.

Sowers and her colleagues found that among the SWAN women, increased FSH levels were
much more predictive of bone loss. This suggests that, in addition to signaling the
ovary, FSH could signal other cells, including bone cells. Bone tissue has been shown
to have receptors sensitive to this hormone, and the levels of rebuilding rate in
bone tissues change in response to FSH levels.

Hormone replacement therapy with estrogen has been effective in stemming bone loss
in some women, but Sowers suspects that his new insight into FSH may help explain
why estrogen’s effects on bone loss vary from one individual to the next.

UM News Service

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